FTB-App VS Launcher

Several users (myself included) are experiencing problems with FTB erroring out when trying to launch an existing modpack or downloading a new one, as evidenced by the last few issues raised on Github. It doesn't look like any of the devs have commented on any of the issues yet, and the only suggestion from other users has been to disable any antivirus software, including Windows Defender, which seems like a terrible idea.

After a certain date(don't know exactly when, although more than a year ago) All FTB modpacks are no longer published or maintained on Curseforge, they are now in the FTB App https://feed-the-beast.com/app and can also be downloaded from launchers with FTB support

After a certain time all FTB packs are no longer published or updated on curseforge, They are all now in the FTB App

Unfortunately, while it's planned, it's not available yet.

I wish i knew what caused that. you could also ask here as well https://github.com/FTBTeam/FTB-App/issues

Feed The Beast Official Launcher FTB modpacks are no longer updated or published on Curseforge

If you cannot - https://github.com/MultiMC/Launcher/wiki/Unsupported-Intel-GPUs

MultiMC

maybe : https://github.com/MultiMC/Launcher/issues/41

Here is a link to Modloader for MCb173. It needs adding directly into the minecraft.jar file, however if you use a launcher like MultiMC, which you can find here: https://multimc.org/ then there is an option to 'add to minecraft jar file' which does the same thing.

I used to have this issue lots, and it was due to my internet being too restrictive. The Minecraft Launcher was refusing to open, and I fixed it by messing with the restrictions until it worked. Hopefully this helps :) if all else fails of course, try just reinstalling it! I’m sure that all your config files don’t get affected by reinstalling it, but just in case make a backup. And if all ELSE ELSE fails, you could switch to a completely different launcher, like MultiMC! Good luck!

If you are willing to try out the launcher - MultiMC which you can find here (there is a Mac option available) : https://multimc.org/ then I have put together an MCb173 pack that has been made for MultiMC. You just use the 'import from zip' option.

Download MultiMC from their official site https://multimc.org/

Others than that, if you insist, you can take a look at the launcher which u/reginakinhi provided or find others on the internet (GitHub for example). Since PrismLauncher is written in C++, and if you are not familiar with it, you should see other launcher as well. Or else https://github.com/MultiMC/Launcher is an alternate.

The best way to experience beta 173 is to play beta 173, and perhaps add some mods to it a little later. One of the better launchers to use for old versions and for playing modded is to use the MultiMC launcher which you can find here: https://multimc.org/

This will only assist if you are using MultiMC as your Minecraft launcher as it is a MultiMC instance which you can use the 'import from zip' option. MultiMC can be found here: https://multimc.org/ It includes IC2 1337 with several add-on mods which have also been back-ported to work with it, such as the Thermometer, Advanced machines, etc. You can disable the add-ons you do not wish included. There is also buildcraft and redpower added as well.